Photothermal-brick for on-site zero liquid discharge treatment of high-salinity wastewater

High-salinity wastewater poses significant treatment challenges due to its complex composition. While photothermal-driven zero liquid discharge (ZLD) technologies offer sustainability, their engineering deployment is often limited by cost constraints and material fragility. To overcome these barriers, we introduce a scalable, durable photothermal-brick (P-B) fabricated from compressed iron tailings, achieving exceptional mechanical strength (26.9 MPa compressive strength) and robustness-withstanding vehicular loads (2-ton SUV) and retaining >90 % strength after simulated aging under laboratory conditions for one year. The P-B enables solar-driven interfacial evaporation for on-site ZLD treatment of high-salinity wastewater. Laboratory tests under simulated sunlight (1 sun, 1000 W m^-2) demonstrated an evaporation rate of 1.65 kg m^-2·h^-1. Crucially, field validation in a 16 m² evaporation pond confirmed scalability and real-world efficacy: 2000 kg of industrial wastewater was processed within 48 h, with peak evaporation rates reaching 6.25 kg m^-2·h^-1 under natural sunlight, enhanced by environmental factors such as wind convection. This work establishes a mechanically robust, industrially viable pathway for solar-powered ZLD, bridging the gap between photothermal innovation and large-scale wastewater treatment.